In the industrial production of monoclonal antibodies and Fc fusion proteins, purification is frequently carried out using affinity chromatography. Protein A from Staphylococcus aureus has long been used as affinity ligand in such applications, due to the native affinity of Protein A for the Fc portion of IgG. Protein A in its entirety, as well as the individual Fc-binding domains thereof, have subsequently served as starting points for the rational design of engineered affinity ligands with improved properties. Despite the comparable success of currently used IgG Fc affinity ligands, there is a continued need for improvement. The continued provision of agents having an affinity for IgG Fc that is comparable with, or higher than, that exhibited by Protein A remains a matter of substantial interest. For example, Protein A affinity chromatography typically uses low pH conditions, which may lead to loss of yield due to the sensitivity of several antibodies and Fc fusion proteins to low pH conditions. The provision of new IgG Fc-binding agents that allow elution at a higher pH as compared to Protein A during affinity chromatography would therefore be beneficial.
It is an object of the invention to provide new IgG Fc-binding agents, that could for example be used in the production of antibodies or Fc fusion proteins, e.g. for affinity separation and/or purification.